NEW MATERIALS OF MASTODONTS FROM THE Y(?)SHE BASIN,SHANSI

New materials of mastodonts from the Yushe Basin,Shansi are preliminarily des- cribed in this paper. One is a new brevirostrine bunolophodon mastodont,under the new specific name Pentalophodon yusheensis.The other is a form of Zygolophodon mastodont,previously described in 1937 by P.Teilhard de Chardin and M.Trassaert as Mastodon intermedius. Summary of the description and comparison of the species. Pentalophodon yusheensis sp.nov. (P1.Ⅰ.Fig. 1,la; Pl.Ⅱ,Fig.1) Specific characters:A brevirostrine mastodont.Cheek teeth rather long and narrow;M_2 consists of four fully developed transverse lophs and a rudimentary fifth loph; M_3 with six transverse lophs and a talonid.Pretrites and posttrites arranged in alter- nating series and directed obliquely with the long axis of tooth.Cingula restricted to the labial side and developed in the form of buttres at the anterior end of tooth. Type:A fairly complete lower,left mandible with well preserved second and third molars(IVPP-V.2876);Paratype——One upper second molar(V.2877).All collected from the Yushe-basin of Shansi. Description:The left mandible is still well preserved,while its symphysial portion and the ascending ramus are completely destroyed. M_2 much narrower anteriorly than the posterior end;pretrites and posttrites much worn and forming polygonal figures;pretrites set obliquely behind the posttrites,and in this manner the alternating arrangement of them is clearly observable.The fifth crest (loph)of M_2 develops uncompletely;in which the pretrites and posttrites consist of each two conules separately.A large central conule situated behind the pretrite of the first loph;after chewing the conule forming a circular ring connecting with the ring of the pretrite. M_3 rather long and narrow;the first two lophs are a little worn after chewing;while the remaining ones are still fresh.The alternating arrangement of the pretrites and post- trites of the first two crests is not clearly observable;from the third to the last crest the alternating arrangement becomes quite distinctly visible. Measurements of teeth in mm: V.2876 Length width Height Index M_2 146 77(3rd.loph) 30(3rd.loph) 52.7 M_3 252 95(3rd.loph) 70(3rd.loph) 37.7 Paratype:M~2,V.2877. One right upper second molar consists of four fully developed lophs and a fifth rudimentary loph,in which 3 conules on the lingual side and one conule on the labial side;lying behind the fifth loph there are a few minute conules.The alternating ar- rangement of the pretrites and posttrites is clearly visible on the posterior lophs of the tooth.There exists a central conule which situated behind the posttrite of the first and the second loph.Cingula restricted to the lingual side and the anterior end of the tooth. Measurement of M~2 in mm:Length—142;Width—76(second loph);Height—40(4th loph). Discussion and comparison: Nowadays the genus Pentalophodon is still rarely known in China.The two species Pentalophodon sinensis and P.cuneatus described by Hopwood(1935)and P.Teilhard de Chardin and Trassaert(1937)were later transfered to the genus Anancus by Osborn (1935),about which Hsieh(1963)had already pointed out.Recently Hsieh described a new species under the name Pentalophodon simplex originated from the district of Pien-Hsien,Shensi province. In comparison with Pentalophodon simplex described by Hsieh the species from Yushe under discussion is quite different.The main points of difference may be sum- marized as follows:(1)M_3 remarkably long and narrow;(2)cones of posttrites directed more obliquely to the main axis of tooth;(3)the molar structures are more complex and advanced than those of Pentalophodon simplex Hsieh. In comparison with Pentalophodon falconeri Osborn(1936,Osborn,Proboscidea, Vol.Ⅰ,p.646,Fig.614)the species of Yushe is also different.The crown of the former is broader;crest number 71/2;central cone larger;number of mammilar cones more numerous(27). In comparison with Pentalophodon sivalensis Cautley(1936 Osborn,p.649,Fig.615; p.625,Fig.618)the new form has the general form of tooth somewhat similar and the pretrites and posttrites and the arrangement of them are,however,remarkably different. We therefore have to deal with a new species,for which the name Pentalophodon yu- sheensis is proposed. Judging from the structure of the number of crests and the exceeding length of the lower third molar,Pentalophodon yusheensis is the most advanced form of mastodonts so far known in China. Zygolophodon intermedius(Teilhard et Trassaert) (pl.Ⅱ,Fig.2,2a). Diagnosis:A brevirostrine mastodont,no trace of lower incisors.Lower cheek teeth elongated;pretrites with traces of trifoils after worn and posttrites sharp and cut- ting. Type:A complete lower mandible,with the two branches of horizontal ramus and the symphysial part preserved,with the third molar in position(V.2878). Description:Crown of the lower third molar elongated,with five transverse lophs;molars are much worn so that the pretrites show only polygonal figures and traces of trefoils;posttrites show strips of rectangles.Cingula restricted to the lingual side of tooth. Measurements of specimen in mm: Length of the horizontal ramus from the posterior face of the ascending branch to the tip of symphysial beak……570 Length of the horizontal ramus from the anterior face of the ascending branch to the tip of the symphysial beak……360 Height of the horizontal ramus(anterior of M_3)……115 Thickness of horizontal ramus(anterior of M_3)……90 Thickness of horizontal ramus(posterior of M_3)……123 Length of the symphysis……130 Internal distance between the two horizontal rami at the anterior of M_3……110 Internal distance between the two horizontal rami at the posterior of M_3……129 Internal distance between the two horizontal rami at the anterior face of the ascending ramus……160 Length of M_3……174 Width of M_3(1st crest)……65 Width of M_3(3rd crest)……70 Width of M_3(5th crest)……39 Height of the crown(3rd crest)……37 The molar structure of the above described specimen is practically identical with that illustrated by P.Teilhard and Trassaert(Pl.Ⅱ,Fig.1 2).Characters of the mo- lars and especially the development of the fifth crest are essentially similar.Besides the characters mentioned above the abbreviation of symphysis and the absorption of the lower tusks belong also the distinguished characters of this species. Locality and geological horizon:Pliocene formations of Yushe-basin,south- tern Shansi.Probably Zone Ⅱ.